


The Devil Inside

by TheSeventhL



Category: Ao no Exorcist | Blue Exorcist
Genre: Angst, Drama, Incest, M/M, Sexual Content, Sibling Incest, Violence
Language: English
Status: Completed
Published: 2012-03-24
Updated: 2012-03-24
Packaged: 2017-11-02 11:44:59
Rating: Mature
Warnings: Graphic Depictions Of Violence
Chapters: 1
Words: 4,071
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/368657
Author URL: https://archiveofourown.org/users/TheSeventhL/pseuds/TheSeventhL
Summary: <blockquote class="userstuff">
              <p>Yukio was the good boy. The smart boy. It wasn't right that he would end up being the cursed one. An AU in which Yukio is the one with demon powers. Yukio/Rin.</p>
            </blockquote>





	The Devil Inside

**Author's Note:**

> Originally written as a response to a Springkink prompt but finished late. The prompt was: "Sept 15 - Ao no Exorcist, Yukio/Rin: AU, protectiveness - Yukio is the one with demon powers."

The hallowed halls of Cross Academy were meant to feel so safe, but as Yukio walks to class, to instruct his pharmacology class, he can feel the eyes of his peers; they look upon him with fear, disgust, and anger. They don't know exactly _why_ they are so angry, other than they've heard the stories of Yukio's suspicious history and how Father Fujimoto died, and that’s enough for people who cross paths with demons on a daily basis. So they look at Yukio and they let him know exactly how wary they are of the bespectacled young man. That is, until Rin saunters up and glares at them with harsh blue eyes (‘better suited to a demon than a human’, Yukio mentally notes with worry) and the onlookers scuttle away, trying to look ashamed that, only seconds ago, they’d been ready to deride Okumura with their unspoken words.

“It’s okay,” Rin says gruffly, hooking one arm across his brother’s shoulders. “They’re just assholes whose parents didn’t teach ‘em any manners. Screw ‘em all!” He casually flips off the crowd that is forming behind them. Yukio is suddenly glad for the blade that hangs at his side, along with his pistols—currently the one true thing, aside from Rin, keeping his emotions in check.

Having Rin at his side, however, in a place dominated by things he’d wanted to save his brother from seeing—does nothing for Yukio's massive guilt complex. He pushes up his glasses with the tips of his fingers and remembers Fujimoto, what he’d done (what his _real father_ had done) and a familiar, sick feeling takes over his head and his heart.

Still, Yukio manages a stern smile in Rin's direction. "Don't antagonize the entire school, brother. We wouldn't want you to be expelled, would we?"

Rin laughs—snorts, more like it, walking with an arrogant strut that is so his. "S'yeah? I'd like to see 'em try and get past me!" He raps the sheath of his own sword with the top of his knuckles; the sword is a twin version of Yukio's own blade, minus the more demonic attributes. "We'll take them on together, right?"

"Let's not get to that point, okay? I'd like to graduate without a major ruckus on my record." Yukio looks amused as his beloved brother keeps strutting it up, pretending he can easily take on an entire school with his one sword, trying not to look as if he isn’t thinking dark wishes. As if he’s not wishing he was alone, that he’d never been born. That at the very least Rin could have kept out of it. 

But life did not work that way. It chose Yukio instead. Not Rin. Not this time.

* * *

_Yukio was the quiet boy, calm and studious. He was the one everyone looked up to while he was in the room, then whispered about when he was gone. He was popular with girls—or at least the ones who didn't know. When they did, he was lucky if they just stopped talking to him altogether. Some of them actually made a big production out of their shock; that usually ended in a giant brawl, because Rin would stick himself into it on Yukio's behalf, and get into fights with their friends until their teachers came and broke them up. Thank goodness for Cross Academy. Thank goodness for at least one place where they could pretend it was normal to have supernatural powers. For a while, at least._

_They said the Okumura family was cursed. Something was wrong with them. No one could ever know the truth—about Yukio, about Rin, about their precious father and his temple of followers who had no idea the dark secret their superior was hiding from them. It wasn't until Fujimoto's untimely death and the secrecy surrounding exactly how it happened that it became apparent how deep in trouble the Okumura clan really was. But no one could figure out how close that trouble was, or the source of it, and especially not how attached to it poor Yukio truly was._

_Of course not; who would have ever guessed Fujimoto's son was touched by Satan himself? Who would have ever guessed sweet, gentle Yukio was a hell spawn in disguise?_

* * *

His dreams are dominated by blood—blood and blue flames that burn him to his core. They engulf him in their heat; they roar through his veins with terrible feelings of hatred and malice and violence. _Kill them all. Burn them. Hurt them. Send them to Hell, for you are the son of Hell itself._

Yukio wakes up on a regular basis in sweat-soaked sheets, heart pounding against his ribcage and feeling like it’ll break out of his chest. In seconds, Rin is at his side. Rin is always at his side. he tries his best to make Yukio feel better, to calm the flames he can feel building up inside his body.

“It’s okay.” Rin’s arms encircle Yukio’s tired body, brushing against the pointed edge of his ears. “I’m here. You’re my brother, okay? We’re together.” Words unsaid: _you’re not a demon to me._

It’s enough for tonight. Yes, even Yukio can admit that this is enough. It is Rin’s body that lies across his with a familiar warmth that doesn’t hurt, and it is enough for now. In the morning, it will be Yukio up at dawn, despite his rough night. Yukio who will have to rouse a sleepy Rin out of bed so he can change the sheets and hustle the both of them to their mundane classes before their daily exorcist training. They won't need to discuss it because it happens so often that it doesn't bear explanation, just acceptance that life sucks and destiny is shit and the best thing they can do is take it on the chin and move the hell on from day to day.

Yukio manages to at least lie down again and get settled back into his wet sheets in a somewhat comfortable position before Rin falls asleep on top of him. It's assuring to know that he's there, asleep but still attentive, in case Yukio thrashes awake before sunrise again. Less so that it is becoming glaringly obvious who is eating all of the leftovers before bedtime, judging by just how much of Rin's weight is pressing into Yukio's side and leaving a Rin-shaped imprint on the mattress below. No, he’ll bring it up tomorrow, and that’s the last coherent thought that slips through Yukio’s usually alert mind before he falls into an exhausted and blessedly dreamless sleep.

* * *

_“Go away.”_

_All of young Yukio’s efforts to push his twin brother away had ended in failure and a series of lectures from Fujimoto about how he shouldn’t reject his brother’s love and that Rin was only looking out for him._

_Even at a young age, Yukio wore glasses. He pushed them up with a quiet sense of dignity better suited for someone twice his age and looked back at the man he called father. “I am capable of being by myself.”_

_Fujimoto sighed; the young boy looked away, despite himself. He hated disappointing his father. “You can’t be alone forever. That’s no way for someone to live.” Even Yukio could understand what Fujimoto meant—that someone like him couldn’t live alone. In turn, the older man knelt beside the boy, his long black habit falling around his feet in waves. “Someday, there will be people who don’t understand you and want to hurt you, and you will want someone to protect you, even for a little bit. And that person will be Rin, because he’s your brother and he loves you. Okay?”_

_Slowly, Yukio nodded. “I understand.” He frowned. “He has to stop stealing my after school snack from the fridge, though!”_

_His father laughed and ruffled the top of Yukio’s head. “I’ll take care of that.” He always took care of the things Yukio couldn’t —or so he thought. Still, in those short still moments of hia youth, with his father’s smiling face and kind hand on his head, Yukio could believe that he was a normal boy who didn’t break the crib in half when he was a baby, or wreck his classroom without realizing, that he was special without being destructive and worthy of being loved by his peers—and by Rin._

* * *

They come in swarms, pick off and separate the ExWires one by one. They have mottled faces and bloody claws and don’t belong here, swooping around and dividing up the pack until all that’s left in the heart of the battle is Yukio Okumura, gun loaded and ready in his hand, sword rumbling impatiently on his hip. _Use me. Use me._

“Kindly keep quiet,” Yukio hisses. “Shut up already.” He’s not used his cursed blade since the day he lost everything—his claim to humanity, his father, his life —and he’s hoping to keep it that way. However, the red-eyed demons swarming the deserted clearing they’ve been using for exorcist training look as though they have other plans in mind for Yukio and his sword.

He clips one in the shoulder as it tries to fly at his face; it falls into a nearby outcropping of rock and bursts into debris, as though it had been made of trash. ‘An abomination,’ Yukio thinks before taking aim and, in quick succession, he shoots down a dozen beasties in the same way. He can hear the others struggling somewhat with their own targets, but he also hears small moments of success—people using their summoning papers properly, someone figuring out the right verse to chant to disable the demons so another can wipe them out completely. If Yukio was the proud type, he’d take a moment to congratulate himself on being a great teacher. Instead, he reloads and keeps firing, taking out five more in under a minute.

Before he has time to call in to the Academy for back-up, something large flashes through the mob of monsters flying through the air and crashes into Yukio, knocking the air out of his lungs. He barely registers one red claw as it enters his side, the sick wet feeling of blood forcefully escaping his body before he hits the ground in a painful skid, kicking up dirt and demon debris in his path.

‘I should have paid more attention—I should have—I should have—it hurts.’ The thing that has crashed into him seconds ago now hangs over him. wet claws dangling at its side in anticipation of digging into Yukio’s flesh a second time—flesh which is now bleeding openly and profusely, sending great sparks of pain throughout Yukio’s chest.

The thing’s voice, dark and gravelly, intrudes into Yukio’s mind without warning. _Silly human boy. You dare venture into my nest and make game of my children? I am the Lord of this land and you shall pay the price!_

Above the sound of the so-called Lord’s children fluttering through the air, hungry for blood, and the pain throbbing across Yukio’s mind, is one distinct wail from a very loud voice. “Yukio! _Yukio!”_

As if being summoned, the Lord turns his head to face in the direction of Rin’s voice, and he laughs. The ugly sound reverberates inside of Yukio’s skull like a gunshot. _I will kill this one too, this blood of your blood that stinks of sin. I will enjoy it very much._ And with that he roars.

“R-Rin! Rin!” Yukio’s usually dignified tone comes out as an unnatural bellow, as if he is pulling his voice out of a deeper, more painful place than usual. He is tired of loss. He is tired of pain. He is tired of seemingly relying on Rin’s strength whenever he’s in trouble. And he is definitely tired of being pushed around.

The sword on his hip feels lighter than ever as he drops the gun from his hand and manages to stand underneath the overhanging form of the Lord above. Flames fill his mouth with an unholy heat and Yukio screams. He can feel his hands reach for the hilt of the sword, and feel the flames rise up through his arm and into his chest because he has temporarily lost control of his sight and all he sees is blue and white and fire—and Rin.

‘I’m sorry…’ and Yukio Okumura is gone. There is only the heir to Satan and wielder of Kurikara, now burning bright in his hands. Even as a demon with his humanity shed, that quiet look of determination is still displayed across the young man’s face. For a few seconds, he looks like the kind and gentle Yukio, until he lunges up into the air, bringing the blade of Kurikara into the monster Lord’s chest and twisting it without mercy, letting the flames grow higher and higher until they enter like blades into the monster’s body.

The heir to Satan is bleeding, but ignores it as he sends his roaring Kurikara straight through the monster, cutting him cleanly in two. He slides away in an impressive jump as the beast’s body falls to the ground where Yukio once lay; what is left of it slowly burning into ashes and debris as Kurikara’s flames eat into its body. 

The children of the thing come at the young man with claws outstretched, intent on spilling some blood themselves. They do not matter to the heir. They are nothing, toys to be batted away without a second thought. And in seconds, they all lie dying at the feet of their superior, bursting into debris at the slightest touch of Kurikara’s steel. 

The wielder of the sword roars, still hungry for death, and he sees there is still one floating excuse of a life form left for him to cut down; it’s trying to hover out of sight to avoid an inevitable death. He lifts his sword up yet again, the blue flames rushing throughout every vein of his body, bursting across with light, but not burning his skin. He is in pain and he wants more than anything to bring pain upon the rest of this terrible world, bring it all crashing to the ground and leave it broken beyond repair, leave nothing alive and walk the ruins alone forever—

Two arms grab him around the middle and, like a light being switched off, the flames begin to extinguish at this oddly familiar touch. A human—a human _boy_ —would dare to touch the rightful heir of Gehenna? He turns in the boy's surprisingly strong grasp and looks into the face of Rin, teeth bared with the effort of keeping him in place.

"Yukio, c-calm down. You have to stop." Rin's words come out between pained gasps for air; the blue flame encircling them both seems to be slowly sucking the oxygen out of their close quarters. "It's over. You totally trashed that asshole, but now you have to come back." 

When Rin's brother speaks, it surprises even him; his voice sounds thin and distant. "Rin. I'm here. You can let go now."

Despite this, Rin shakes his head as vigorously as possible and bares his teeth in defiance. "No, I won't. Not until every last flame is gone—not until I see that Yukio is back here with me. Not until my brother is in front of me again!" Rin's protective attitude, like a parent telling his child he _must_ finish every little thing on his plate, makes the demon laugh a little, and in this moment of weakness the demon melts away until all that is left is the human—vulnerable and very much alive.

The heir to the throne of Hell twists and turns in the other man’s grasp until the blazing blue light dies down and the demonic persona melts away—and then there is only Yukio Okumura, collapsing in the arms of his brother Rin, sword on the ground and no longer spewing fire from its blade.

Yukio breathes in the earthy _clean_ smell of his brother, his twin, and realizes that Rin is covered in bleeding cuts and bruises leftover from the clawed demons that had attacked only moments ago. It seems like centuries. No one notices the last little demon fly away frantically into the sky, but they do hear the sound of one of Izumo's summoned foxes ripping into it, finishing the thing off.

"Rin, you're hurt. Let me—He reaches for his pharmaceutical bag but it's not there; it must have flown off during the fight with the demon Lord. Rin stops his hand anyway.

"Don't worry about me. The others—they're still out there—let's go help them, okay?" Rin nods and does a terrible job of hiding the wince of pain that accompanies his movement.

It’s almost laughable. Yukio is the teacher and yet Rin has to be the one who tells him what to do. He feels weak, physically and mentally. He feels ashamed of losing control and nearly causing his brother harm. But he still accepts Rin's hand that pulls him up off the ground, and still lets him send up the flare for the other students to see and return to. But Yukio does find his pharmacy bag himself, lying several feet away from where the Lord had tackled him, and he’s grateful to see nothing is damaged beyond repair. He manages to use some of the medical items inside to bring his brother back to health—or at least healthy enough to make the long trek home. He does not look Rin in the face as he does so, letting his hands fill in the silence between them.

Seconds later, his students return, all sporting the aftereffects of an unexpected battle won, and Yukio manages to compose himself long enough to escort his ExWires back to campus for a debriefing and then dismissal for the rest of the day. He doesn’t look Rin in the eye even once as he does all of this; he doesn’t deserve to, after losing control like that—practically exposing himself to his students!—and this is made only more awkward by their joint return to the dorms where luckily (or unluckily) no certain noisily flamboyant persons named Mephisto are waiting to question them about the day’s failed training exercise. His sword weighs heavy on his back.

"Rin." Yukio puts his hand on Rin's shoulder to stop him in his tracks; he owes an explanation to the other man. An apology for his unwonted nature, although words would never be enough. "I—I'm sorry. I let you down."

Rin turns away, twists his shoulder out of Yukio's grasp. He does not look Yukio in the face. "Shut up."

"Rin." Yukio sounds pathetic, even to himself. He nods. "I understand. I was supposed to control myself but I put everyone at risk—I put you at risk—and I don't deserve your trust anymore. I should do the right thing and leave. I can't risk putting innocent people in danger again."

"Shut up!" Rin turns around to face Yukio, and in the moonlight spilling from the window high above their heads, Yukio can see the mix of emotions across his brother's face: anger and sadness and something indescribable, almost like guilt. "You idiot, I don't care about any of that! I just care if you get hurt!" Rin's typical scowl is more like a frown. "I want to be there every time, to make sure you don't get yourself in trouble."

Yukio is temporarily taken aback by Rin's fierceness. But he also can't take his brother's anger seriously. Yukio brushes past Rin, though the effort makes his chest ache. He's gotten so used to turning his back on his beloved brother, trying to stay alone. And here he is, doing it again. It hurts him, but he feels he has to do it. 

"This isn't up to you. It's my decision—and clearly things have gone too far." Yukio sighs. "I can't control myself. I—I must take responsibility for what I am and what I’ ve become."

A second later, he's seeing stars and falling back against the wall, nearly knocking down a portrait in the process. He blinks and sees his brother's open hand still in the air, the hand that knocked him back, and the look of agitation on Rin's face.

"We're supposed to be brothers." Rin's mouth twitches as if he’s going to add something else, but instead he turns on his heel and walks off in the direction of his own room, leaving Yukio alone on the floor.

He flicks his tongue across his lips and tastes blood still lingering from the earlier yokai hunt. His blood. Rin's blood. The other's words still echo in his head, desperate and raw with emotion. _We're supposed to be brothers._ Rin is right. They are the same, both sons of Satan, both doomed to be alone in a world that will never understand what they are. It just happens that Yukio has taken the brunt of their father's cursed powers instead of Rin, the winner of some twisted lottery he never wanted to play.

Yukio swallows an herbal pain pill down before stumbling off to bed, treading carefully across the floor as to not disturb Rin. He ignores the aching in his bones long enough to lock away the sword Kurikara in his closet. He does not want to see it anymore, or feel the need to rely on it while he sleeps. His bed is already occupied when he tries to climb in. Yukio tries to sneak out without a sound, but a familiar hand draws him in between the blankets, one arm winding around his middle. Still fully dressed, he allows himself to fall asleep in Rin's possessive grasp.

Early morning light falls through an open gap in the curtains, falling upon a sleeping mass wrapped up in blankets and tussled sheets. Yukio opens his eyes, waking up slowly, and he is not alone.

“Yukio-san. . .” Rin mumbles his brother’s name in his sleep, a line of drool falling from the corner of his mouth and across his pillow.

He sets his hand across Rin’s hair, lightly. “It’s okay,” Yukio says, not loud enough to wake the other boy. They will talk about it later—their parentage, Yukio’s powers, and their future together. It will not be perfect, but it will be something. For a moment, he lies there in bed, still hung up in Rin’s limbs, watching his brother sleep. His eyes wander towards the place where he’s locked away his sheathed Kurikara.

Fujimoto, have I failed you? Yukio sighs. His breath sends several strands of Rin’s hair flying across his forehead. Someday, he’ll let Rin protect him, just once. Not because he needs it, but because he loves Rin too much to not let him anymore—and because he loves Rin too much to let them both be alone.

A slow mumble that sounds like a _good morning_ draws his attention back to the bed. Yukio looks down in time to see Rin sleepily tug on his sleeve with his free arm, pulling the older brother down on top of him. There is a mess of limbs floating about and weighing down on each other. A pair of hands runs through dark hair, a knee pressing dangerously close into the more sensitive curves of Yukio's legs. This has happened before; this is how Rin and Yukio make up these days, through the heaviness of their bodies and the quickness of their hands. In the early morning light, Yukio can see his brother's face flushed with pink, his mouth straining to contain all of the gasps and moans eager to come out as the other boy's hands move lightly through fabric and waistbands.

The older brother soon forgets his problems and remembers only how much he loves Rin, how much he wants to be consumed by his younger other half and to forget the darker side of the one called Yukio exists. He is a demon, a curse on his family, but Rin makes him remember there is still a better version of him alive.

Yukio leans in further, dipping his mouth down to meet Rin's. His brother tastes of blue fire and it burns him. He tastes the fire and is consumed by it. In the end, they are both cursed.


End file.
